Default --lookup-extents option value to no again

The default for `--lookup-extents` was set to `no` in e1c8950b2e09fb3ac810a5f48b581e4b350c7ef9, but regressed to `yes` in 1b77385f1ec28a145e6a2305561d149a7e1eb1e1.

The commit in this PR sets this back to "no" to match the information in `duperemove.8`